from dynamic$\_$array import $*$

class StackException$($Exception$)$:

$"""$

Custom exception to be used by Stack class

DO NOT CHANGE THIS METHOD IN ANY WAY

$"""$

pass

class Stack:

def $\_\_$init$\_\_($self$)$:

$"""$

Init new stack based on Dynamic Array

DO NOT CHANGE THIS METHOD IN ANY WAY

$"""$

self.$\_$da $=$ DynamicArray$()$

def $\_\_$str$\_\_($self$)->$ str:

$"""$

Return content of stack in human$-$readable form

DO NOT CHANGE THIS METHOD IN ANY WAY

$"""$

out $=$ "STACK: $"+$ str$($self$.\_$da$.$length$())+"$ elements. $["$

out $+=\text{'},\text{'}.$join$([$str$($self$.\_$da$[$i$])$ for i in range$($self$.\_$da$.$length$())])$

return out $+\text{'}]\text{'}$

def is$\_$empty$($self$)->$ bool:

$"""$

Return True is the stack is empty, False otherwise

DO NOT CHANGE THIS METHOD IN ANY WAY

$"""$

return self.$\_$da$.$is$\_$empty$()$

def size$($self$)->$ int:

$"""$

Return number of elements currently in the stack

DO NOT CHANGE THIS METHOD IN ANY WAY

$"""$

return self.$\_$da$.$length$()$

# $-----------------------------------------------------------------------$

def push$($self$,$ value: object$)->$ None:

$"""$

TODO: Write this implementation

$"""$

pass

def pop$($self$)->$ object:

$"""$

TODO: Write this implementation

$"""$

pass

def top$($self$)->$ object:

$"""$

TODO: Write this implementation

$"""$

pass

# $-------------------$ BASIC TESTING $-----------------------------------------$

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

print$("$

# push example $1")$

s $=$ Stack$()$

print$($s$)$

for value in $[1,2,3,4,5]$:

s$.$push$($value$)$

print$($s$)$

print$("$

# pop example $1")$

s $=$ Stack$()$

try:

print$($s$.$pop$())$

except Exception as e:

print$("$Exception:$",$ type$($e$))$

for value in $[1,2,3,4,5]$:

s$.$push$($value$)$

for i in range$(6)$:

try:

print$($s$.$pop$())$

except Exception as e:

print$("$Exception:$",$ type$($e$))$

print$("$

# top example $1")$

s $=$ Stack$()$

try:

s$.$top$()$

except Exception as e:

print$("$No elements in stack", type$($e$))$

s$.$push$(10)$

s$.$push$(20)$

print$($s$)$

print$($s$.$top$())$

print$($s$.$top$())$

print$($s$)$